Means for reducing pressure in packing boxes of pumps



QED W 3%? 5-5. A. $.JOHAN5SON fifiggygwgi MEANS FOR REDUCING PRESSURE IN PACKING BOXES OF PUMPS Filed July 15. 1965 3,296,974 Patented Jam. 10, 1967 3,296,974 MEANS FOR REDUCING PRESSURE IN PACKING BOXES F PUMPS Sven Allan Sigvard Johansson, Lidiugo, Sweden, assignor to Sunds Verkstader Aktiebolag, Sundsbruk, Sweden Filed July 15, 1965, Ser. No. 472,251

Claims priority, application Sweden, July 16, 1964,

8,693/ 64 3 Claims. (Cl. 103-126) In known types of pumps, particularly of the kind serving for the transfer of sluggish materials, such as cellulose pulp of 6-25 consistencies, the shaft ends of the pump wheels or of the rotors are subject to too rapid a wear, because of the cellulose pulp being pressed into the packing boxes, where it is dehydrated and, hence, will exert a considerable wearing action. Efforts have been made to eliminate these drawbacks by connecting pressurized water to the packing boxes, such water being of a higher pressure than the one prevailing on the driving side of the pump. This measure has resulted in a slower wear but nevertheless the length of life of the pumps has not become satisfactory.

The object of the present invention is to eliminate these drawbacks by reducing the pressure all around the shaft end adjacent to the packing box. The rotor end, which may be arranged to seal against the pump housing with the least possible play is, for that purpose, provided with one or more recesses, such as grooves or channels, which are arranged to be continuously or intermittenly, in a draining communication with the lowpressure side of the pump. The pulp, pressed in between the end surface of the rotor and the wall of the pump housing, will then be trapped by the recess, or recesses, provided in the end of the rotor, and then, through said draining communication, move to the low-pressure side of the pump.

It is suitable to provide the rotor end with a groove or channel, extending around, preferably all around, the rotor shaft and, preferentially, concentrically with said shaft, and said draining communication may consist of a duct, provided in the wall of the pump housing turned toward the rotor end, said duct extending radially outwards to the low-pressure side of the pump. In order to safeguard that the grooves or channels shall not become choked up, a pin or the like provided in the wall of the pump housing may, with a slight play, extend into the groove, or channel, of the rotor and the groove or channel of the housing may be made relatively wide. It is convenient to provide said pin immediately after said last-mentioned groove or channel with respect to the direction of rotation.

A more detailed description of the invention will follow below, reference being had therein to the accompanying drawing, FIGS. 1 to 3, which illustrate one embodiment of the invention, said embodiment, however, in no way limiting the scope of the invention.

FIGS. 1 and 2 show a pump of the gear type, intended for, for example, cellulose pulp. The pump comprises a housing 1, within which two rotors 2 are mounted to rotate counter each other while sealing, with blades 3, against the longitudinal walls 4 of the housing and against valleys 5 in the rotors. The sealing between the rotors may also be obtained by means of projecting portions 6, which are located at a smaller distance away from the rotor shaft than the blades 3. One rotor is driven directly from the shaft 7 and the other through the intermediary of the gear drive 8, which also serves as synchronizing means for the rotors.

When pulp is being supplied to the low-pressure chamber of the pump, said pulp will fill up the compart- United States Patent Ofiice ments between the blades 3 and, during the rotation of the rotors, it will be transferred, gradually, into the high pressure chamber '10 along the longitudinally extending walls 4. A considerably smaller quantity of the pulp is returned to the low-pressure chamber through the compartments formed between the rotors. In the high-pressure chamber it is often desired to maintain an overpressure of 2 to 3 kg./sq. cm., due to which the rotor shafts 7, 11 must have efiicient sealing means with respect to the end walls 12 of the housing 1. Despite said sealing arrangement in hitherto known constructions of this kind it is possible for cellulose fibers to penetrate and to be pressed int-o the packing box 16, which is provided in the rotor casing for the purpose of sealing all around the rotor shaft 7.

For the purpose of overcoming this drawback the end surfaces 13 of, preferably, both rotors are, in accordance with the present invention, provided with a groove or channel 14 extending all the way around, said groove or channel, in the embodiment shown, being concentric with the rotor shaft. Siaid groove or channel 14 may be located near the outer periphery of the end surface, as shown in the drawing, or it may be positioned nearer to the inner periphery of the end surface. One suitable arrangement consists in providing said groove or channel so near to the axis of the rotor that the inner cylindrical bordering surface of the groove or channel 14 is formed by the shaft 7 and the shaft 11, respectively. Said groove or channel 14 in the end surface of the rotor has a draining communication with the low-pressure chamber of the pump through a groove or channel 15 in the end wall 12 of the housing. Hereby the pressure will be reduced all around the shaft at the packing box 16 and thereby V the risk of fibers penetrating into the packing box has become reduced substantially. To safeguard still further against wear of the shaft within the box pressurized water may, in a known manner, be supplied to the box through the duct 117.

For the purpose of cleaning the groove or channel '14, a pin or the like 18 may be provided, said pin extending into said groove or channel, as shown in FIGS. 1 and 3. In a suitable manner said pin 18 is fixed to the end wall 12 of the pump housing and it is preferred to provide the pin immediately after the groove or channel 15 with respect to the direction of rotation. Hereby the groove or channel 14 is prevented from being choked up, the width of said groove or channel preferably being smaller than that of the groove or channel 15. It is of advantage to arrange said pin in such a manner that it can be inserted and/or be replaced from outside the housing or from inside the packing box.

The arrangement according to the invention may be modified in several ways within the scope and nature of the invention. For instance, in certain cases the groove or channel 14, which is annular and unbroken, may be replaced by a series of interspaced recesses, for instance, in the shape of bores, or holes, which are arranged to be put into draining communication with the low-pressure side of the pump as they pass said side. Furthermore, the groove or channel 15 may be replaced by a pipe extending wholly or partly outside the pump housing from the groove or channel in the rotor to the space, or chamber, at the lowpressure side of the pump, or possibly to some other space, or chamber, outside the pump. Instead of providing a pipe of the kind mentioned it is also possible to cast the housing with a duct having openings at the same places as those of the pipe. In these embodiments the outer end surface of the rotor may seal all the way around with a small play, which is not the case in the embodiment described, in which the sealing is broken by the groove or channel 15.

Furthermore, it is possible to have the pipe extend some distance into the housing and bend in the direction of feed of the pulp, by which the opening will be protected from the flow of pulp in the housing and the risk of choking up being still more reduced. The same effect may be obtained by providing a screen before the groove or channel 15. It is also to be observed that the reduction of pressure may be obtained in several steps by providing the end of the rotor with several concentric grooves or channels, each communicating with its separate drain duct.

Having now described my invention, what I claim as new and desire to secure by letters patent is:

1. A pump for pulpy material, such as cellulose pulp, comprising a pump housing with a pump rotor provided therein and substantially axially extending blades for the transfer of material from the low-pressure side of the pump to the high-pressure side thereof, at least one of the end walls of the rotor sealing, with the least possible play, against an adjacent wall of the pump housing through which extends the shaft of the rotor, at least one groove being provided in the end wall of the rotor and extending around the shaft of the rotor, said groove being arranged to be put into draining comrmunication with the low-pressure side of the pump for preventing high pressure fluid from the high pressure side of the pump from reaching the packing box for the shaft of the rotor.

2. A pump as claimed in claim 1, in which said draining communication consists of a groove provided in the pump housing.

3. A pump as claimed in claim 1, in which a memher is provided for cleaning the groove in the end wall of the rotor.,

References Cited by the Examiner UNITED STATES PATENTS 1,096,186 5/1914 Nesmith 103126 2,321,609 6/1943 Marco 103-426 3,191,540 6/1965 Skretting 103--126 DONLEY J. STOCKING, Primary Examiner.

WILBUR J. GOODLIN, Examiner. 

1. A PUMP FOR PULPY MATERIAL, SUCH AS CELLULOSE PULP, COMPRISING A PUMP HOUSING WITH A PUMP ROTOR PROVIDED THEREIN AND SUBSTANTIALLY AXIALLY EXTENDING BLADES FOR THE TRANSFER OF MATERIAL FROM THE LOW-PRESSURE SIDE OF THE PUMP TO THE HIGH-PRESSURE SIDE THEREOF, AT LEAST ONE OF THE END WALLS OF THE ROTOR SEALING, WITH THE LEAST POSSIBLE PLAY, AGAINST AN ADJACENT WALL OF THE PUMP HOUSING THROUGH WHICH EXTENDS THE SHAFT OF THE ROTOR, AT LEAST ONE GROOVE BEING PROVIDED IN THE END WALL OF THE ROTOR AND EXTENDING AROUND THE SHAFT OF THE ROTOR, SAID GROOVE BEING ARRANGED TO BE PUT INTO DRAINING COMMUNICATION WITH THE LOW-PRESSURE SIDE OF THE PUMP FOR PREVENTING HIGH PRESSURE FLUID FROM THE HIGH PRESSURE SIDE OF THE PUMP FROM REACHING THE PACKING BOX FOR THE SHAFT OF THE ROTOR. 